Clamp for industrial trucks



May 11, 1954 0. WIGHT, JR 2,678,141

CLAMP FOR INDUSTRIAL TRUCKS Filed June 29, 1950 5 Shegts-Sheet 1 INVENTOR. DELANO WIGHT JR.

ATTYS.

D. WIGHT, JR

' CLAMP FOR INDUSTRIAL TRUCKS May 11, 1954 5 Sheets-Sheet 2 Filed June 29, 1950 aq-a;

IN VEN TOR. DELANO WIGHT JR.

ATTYS.

May 11, 1954 D. WIGHT, JR 2,678,141

CLAMP FOR INDUSTRIAL TRUCKS Filed June 29, 1950 5 Sheets-Sheet 3 DE L.ANO WIGHT JR.

ATTYS.

May 11, 1954 D. WIGHT, JR

CLAMP FOR INDUSTRIAL TRUCKS Filed June 29. 1950 5 Sheets-Sheet 4 FIG. 4

INVENTOR. DELANO WIGHT JR.

May 11, 1954 Filed June 29. 1950 D. WIGHT, JR 2,678,141

CLAMP FOR INDUSTRIAL 'mucxs 5 Sheets-Sheet 5 FIG. 6

DELANO WIGHT JR.

ATTYS.

Patented May 11, 1954 CLAMP FOR INDUSTRIAL TRUCKS,-

DelanoWight, Jn, Battle Creek, Mich, assignor to Clark Equipment Company,

Buchanan,

Mich, a corporation of Michigan Application June29, 1950, SeriatNo. 170,967

11 Claims. 1

My invention relates generally to load engaging means for industrial trucks and, more specifically, is directed to clamp means adapted to. engage the upper horizontal projecting edge of a crate, carton, or container.

It is an object of my present invention to. pro-, vide clam means which is adaptedtobe mounted to the load supporting carriage of an industrial truck for engaging the upper horizontal projecting edgeof a crate, carton, or container whereby the latter may be transported, stacked, and deposited by the industrial truck.

In the preferred embodiment of my invention I contemplate the -provision. of vertically extend: ing main frame means adapted to be mounted to the load supporting carriage of an industrial truck transversely thereof. Mounted to and vertically above the main frame means is secondary frame means which is adapted to carry movable jaw means, which preferably comprises, a pair of jaw members. Means for moving. the pair of jaw members toward and away from the upper edge of the main frame means'is carried. by. the secondary frame means and may, for example, comprise a pair of hydraulic piston and cylinderassemblies. When the projecting edge of a crate or container is disposed between the movable jaw members and, the upper edge of the main frame means, the former is urged toward the latter whereby the projecting edge of the crate or container is securely clamped therebetween. The.

crate or container may then be raised from the ground by effecting upward movement of the load supporting carriage of the industrial truck. After the carton or container has been raised from the ground it is supported by the clamp, jaws, with a portion of the downward force ex; erted by the weight of a load within the crate or container being taken by the main frame means, against which the crate or container is adapted to bear.

In a modified form of my present invention for accomplishing the aforementioned object, I contemplate the provision of vertically extending frame means adapted to be mounted to the load supporting carriage of an industrial truck tran se versely thereof. Horizontally extending fixed jaw means is secured to the frame means adja, cent the upper end thereof, and horizontally ex-. tending movable jaw means, carried by the frame means, is disposed vertically below the fixed jaw means. Means for moving the movable jaw means toward and away from the fixed jaw means is carried by the frame means and may, for example, comprise a hydraulic piston and cylinder assembly preferably disposed within the confines of the, frame means. After the projecting edge of a crate or container has been clamped between the fixed and movable jaw means and the carton or container raised from the ground, the latter is supported by the clamp jaw means, with a portion of the downward force,

framemeans.

I propose to accomplish this object by slidably mounting load engaging frame members to the frame means, adjacent each side thereof, along the lower edge thereof. It will thus be realized that when the load engaging frame members are spread laterally outwardly of the frame means, that improved bearing. support is provided for a crate or container which is of greater transverse extent than the frame means.

Now, in order to acquaint those skilled in the, art with the manner of constructing and using the devices of my present invention, I shall describe, in connection with the accompanying drawings, certain preferred forms of my invention.

In the drawings:

Figure 1 is a perspective view of an industrial truck to which, at the forward end thereof, is secured the preferredfor-m of clamp construction of my present invention;

Figure 2 is a front view of the clam construction of Figure 1;

Figure 3 is a side elevational view of the clamp construction of Figure 1;

Figure 4 is a front view of a modified form of clamp construction of mypresent invention;

Figure 5 is a side elevational view of the clamp construction of Figure 4;

Figure 6 is a front view of another modified form of clamp. construction of my present invention;

Figure 7 is a side elevational view of the clamp construction of Figure, 6; and

Figure 8 is a front view of a pair of clamp constructions, of the form shown in Figure 6, disposed in side by. side relation.

Referring now to Figures 1 through 3 of the drawings, there is shown a preferred form of clamp construction of my present invention attached to an industrial truck, indicated generally by the reference numeral [5, having forward driving wheels H and rear steering wheels l2. A steering column 13, including a hand steering wheel M, is provided adjacent the forward end of the truck H3 and is adapted to be manipulated by an operator of the truck for steering the latter. The truck It is powered by a suitable prime mover, as, for example, an electric motor (not shown) having suitable connection, through drive means (not shown), to the forward driving wheels H. A conventional foot brake pedal is indicated at I5. Suitable control levers are provided at l5 and ll for effecting operation of the various devices of the industrial truck Ill.

Pivotally mounted adjacent the forward end of the truck it, about an axis extending transversely thereof, is a substantially vertically extending conventional mast, indicated generally at It, comprising two pairs of vertically extending channel members of which only the outer pair l9l 5 are readily discernible in Figure l. Interconnecting the upper ends of the channel members Iii-59 is a crosshead which supports a' pair of spaced apart sprocket gears 2l--2I, over which chains 2222 are trained. The chains 22-22 are secured at their one ends to a cross brace member 23 interconnecting the inner channel members of the mast It. The other ends of the chains 22-22 are secured to a conventional load supporting carriage (not shown), mounted for vertical movement within the mast I8.

Suitably secured to the load supporting carriage is a vertically extending plate member 25. Attached to the plate member 25 is a preferred form of clamp mechanism of my present invention. The clamp mechanism comprises a vertically extending plate member 26 having a vertical plate member 2? of shorter lengthwise extent secured to the upper edge thereof in the same plane. The plate 2i has a pair of vertically extending openings Zla formed therein for a purpose to be hereinafter described. A. vertically extending bar 28 is suitably secured, as by welding, adjacent its lower end to the upper edge of the plate member 2?, intermediate of the ends thereof. Secured, as by welding, intermediate of its ends, to the upper edge of the vertical bar 28 is a horizontal crossbar 29 which lies in the same plane as plate members 26 and 2?. Interconnecting the respective ends of plate member 2'! and crossbar 29 are a pair of vertical angle members 35 and 3 l.

The aforedescribed frame construction of the clamp mechanism is secured to the vertically extending plate member 25, carried by the load supporting carriage of the truck ill, by means of inverted hook-shaped bracket members 32, which are disposed in engagement with the upper edge of the plate member 25. The clamp frame construction is also mounted to the plate member 25 by means of upturned hook-shaped bracket members 33 which are disposed in engagement with the lower edge of the plate member 25. The upper bracket members 32 are suitably secured to the plate member 21, as by welding, while the lower bracket members 33 are detachably mounted to the plate member 25 by means of bolts 35a. From the foregoing description it will be realized that the clamp construction of my present invention may be easily and speedily secured to or detached from the plate member 25, in order that other load engaging devices may be mounted thereto. s

Suitably secured to the forward surface of the plate member 26, adjacent the upper and lower ends thereof, are a pair of horizontally extending parallel spaced apart bar members 35 and 36. The bar members 35 and 36 provide a support for a substantially vertically extending load engaging sheet member or platen 31, which is secured thereto by means of a plurality of bolts 38.

Mounted to the forward vertical surface of the horizontal crossbar 29, adjacent each end thereof, are a pair of bracket members 49 and M, to which, respectively, are pivotally mounted, about pins 50a and Ma, the closed ends of cylinders 44 and d5 of a pair of vertically downwardly extending hydraulic piston and cylinder assemblies 42 and 53. The outer'end of the piston rod 46 of the hydraulic piston and cylinder assembly 42 is pivotally mounted, by a pin member 54, between block members 48 and 52, and the outer end of the piston rod 47 of the hydraulic piston and cylinder assembly 43 is pivotally mounted, by a pin member 55, between block members 49 and 53. The block members 52 and 53 are suitably secured to the upper edges of a pair of clamp elements or jaws 50 and El. The block members 48 and 59 are disposed in the aforedescribed openings 27a in the plate member 2'! for guiding vertical movement of the clamp jaws 5B and 5 l Suitable fluid lines 56, leadnig from a hydraulic fluid pump (not shown), carried by the industrial truck ill, are connected to the upper ends of the cylinders 55 and 45 of the hydraulic piston and cylinder assemblies 42 and 43. A second pair of fluid lines 57, leading from the hydraulic fluid pump, are connected to the lower ends of the cylinders 4d and 45. The control lever H is inter connected betwen the hydraulic fluid pump and the fluid lines 55 and 5'! for permitting the operator of the truck 10 to selectively admit fluid either to the upper ends of the hydraulic piston and cylinder assemblies 52 and 43 or to the lower ends of the cylinders 44 and 45. When fluid under pressure is admitted through the fluid lines 55 to the upper ends of the cylinders 44 and 45, the piston rods 45 and 41, and their respective jaw members 55 and 5 l, are extended downwardly into engagement with the fixed clamp element or jaw member 35. When fluid under pressure is admitted to the lower ends of the cylinders 44 and 55, through lines 57, and lines 55 are bled, the piston rods 36 and 41, together with their respective clamp jaws 5t and 5|, are retracted upwardly away from engagement with the fixed jaw member 35.

The clamping device described above is particularly adapted for engaging a lip or leading edge of a cardboard container provided along one side, adjacent the upper horizontal edge thereof. My present clamp construction obviates the necessity of stacking cardboard containers, filled with goods, on top of pallets in order that they may be transported by an industrial truck, and further renders unnecessary the use of conven tional forwardly extending fork members.

When a load is gripped between the clamp elements 55 and 5! and clamp element 35, the load bears against the load engaging sheet member 37. It will be understood that other forms of load engaging surfaces may be utilized so long as the surface prevents rocking movement of the load when in gripped position.

In the use of the clamping device of my present invention, the truck I!) is lined up directly in front of a container having a laterally projecting lip or leading edge. The operator then operates the control lever at H, effecting adaczcgmr mission of fluid under pressure to the lower ends of the cylinders 44 and through hose lines 51, which urges the: piston rods 46 and 41 upwardly, together with the jaw members 551 and 5|. Then the plate member 25, together with the clamp construction, is adjusted vertically within the mast i8 until the opening between the movablejaw members 5!] and 5i, and the fixed jaw-member 35 is substantially in alignment with theprotrud-ing lip member on the container to be picked up. The truck ill is then driven forward until the protruding lip member on the container is disposed between the movable jaws 59 and 51- and the fixed jaw member 35. The operator then manipulates the control lever I! and places lines 5'! under bleed and lines 56 under pressure, which admits fluid to the upper ends of'the cylinders 44 and 45, urging the piston rods 46 and 41- downwardly, together with clamp jaws and 5|. clamp jaws 50 and 5| firmly clamps the protruding edge of the container between the movable jaws 50 and 5| and the fixed jaw member 35; The plate member 25, together with the clamping mechanism and load, may then be raised within the mast and the truck driven away tothe location in which the containers are to be deposited. Then the reverse procedure, as outlined above, is followed. That is, the truck is maneuvered until the container is in the desired l'Ocation. Then the plate member 25, together with the clamping mechanism and load, is lowered until the container contacts the ground. The operator then manipulates the control lever at; H, placing the lines 56 under bleed and admitting fluid under pressure, through lines 51, tothe lower ends of the cylinders 44 and 45, causing the piston rods 46 and 47-, together with the clamp, jaws 50 and 5!, to retract upwardly, thereby releasing the protruding lip of the con-- tainer from between the movable jaw members and 5| and the fixed jaw member 35.

While, in the above description, the clamp construction of my present invention has been described as engaging and supporting a single container, it will be realized that an entire tier of containers, if within the weight supporting capacity ofthe truck, may be transported by clamping the leading edge of the lowermost container between the movable clamp jaws 50 and 5| and the fixed jaw member 35.

Referring now to Figures 4 and 5, there is shown a modified form of clamp mechanism of mypresent invention. This form of my invention, like the preferred embodiment described above, is adapted to be secured to the load supporting carriage of the industrial truck Ill. The clamp mechanism comprises a vertical transversely extending plate member 10 to which, at the rear surface thereof, is secured a supporting plate member H. The plate member H has secured to it rear surface a pair of spaced apart inverted hook-shaped bracket members 12 which are adapted to be disposed over the upper edge of a transversely extending frame member carried by the load supporting carriage of the industrial truck l0. Secured along the lower edge of the rear surface of plate member II, as by bolts 14, are a pair of spaced apart upwardly extending hook-shaped support bracket members 13'. The bracket members 13 are adapted to be disposed in engagement with the lower edge of the transversely extending frame member carried by the load; supporting carriage of'the truck it.

Suitably secured alongthe upper edge of the The downward force exerted on the 6w plate member 10 is a horizontally extending, fixed clamp element or jaw member 15. Secured to the. front surface of the plate member 10, adjacent, each side thereof, are a pair of vertically extending forwardly projecting strap members 71.

- indicated generally by the reference numeral 81.

The hydraulic piston and cylinder assembly Bi has a piston rod. 82 which is adapted to be ex-. tended and retracted vertically. The upper end of the piston rod 82 is flexibly mounted within a transversely extending movable clamp element or jaw member 85, which is adapted to be moved.

toward and away from the fixed upper jaw member 15, A slot 85 is formed in. the plate member it and a boit 64 is disposed therethrough, and threaded into the movable jaw 85, for guidingv the latter in vertical movement. In order to maintain the lower jaw member 85 parallel to the fixed jaw it, a guide pin 3'! is mounted in the lower jaw member 85 below the bolt $6. The guide pin 81 is adapted to project into the vertical slot 8t formed in the plate member '18. The guide pin 8?, like the bolt 54, is adapted to slide vertically within the slot 88 when the piston rod 82 is extended or retracted.

The rear supporting plate H has a U-shaped cutout Ell, adjacent the upper end thereof, which cutout is provided for receiving the head of bolt 3 when the movable jaw 85 is in its retracted position, as shown by dotted lines in Figure 5.

A pair of openings 91 are formed in the plate member 59' adjacent each side of the hydraulic piston and cylinder assembly at. Fluid hose lines (not shown) are adapted to be disposed through the openings 91 for connecting the hydraulic piston and cylinder assembly 3! with a source of fluid under pressure.

The mating surfaces of the fixed and movablejaw members 15 and 85 are adapted for engaging the leading edges or lips of cardboard containers. It will be understood, however, that the clamp construction of my present invention is also adapted for gripping the projecting edges of other forms of containers, as, for example, the end boards of wooden crates.

Whenthe leading edge of a container is gripped between the fixed and movable jaws l5 and 85 of the clamp construction, the vertically extending side of the container, adjacent the clamp construction, is adapted to bear or rest against the plate member 13.

Referring now to Figures 6 and 7, there is shown another modified form of the clamping mechanism of my present invention. This form of my invention, like the previous forms described, is adapted to be secured to the load supporting carriage of the industrial truck iii. The clamping mechanism comprises a vertical transversely extending plate ill! to which, at the rear surface thereof, is secured a supporting plate Interconnecting the forward edges of the strap members 11 is a load engaging plate mem-,

Openings 95 are member I'I'i. The plate member I'Il has secured to its rear surface a pair of spaced apart inverted hook-shaped bracket members I12 which are adapted to be disposed over the upper edge of a transversely extending frame member carried by the load supporting carriage of the industrial truck IO. Secured along the lower edge of the rear surface of plate member Ill, as by bolts I14, are a pair of spaced apart upwardly extending hook-shaped bracket members Il3.. The bracket members I13 are adapted to be disposed in engagement with the lower edge of the transversely extending frame member carried by the load supporting carriage of the truck I0.

Suitably secured along the upper edge of the forward surface of plate member Ilil is a horizontally extending fixed clamp element or jaw member H5. Secured to the front surface of the plate member I'lil, adjacent each side thereof, are a pair of vertically extending forwardly projecting strap members Ill. The strap members I'I'l terminate short of the bottom of the plate member Ilil. Interconnecting the forward edges of the strap members ill, adjacent the lower end thereof, is a load engaging plate member I18 which is secured to the strap members Ill by a plurality of screws I'iiia. Openings I'Ha are formed in the plate member Il8 forwardly of the bolts Il i in order that access may be had to the latter for removing the brackets H3 should it become necessary to remove the clamp construction from the truck It.

Pivotally mounted to the forward surface of the plate member ill), adjacent the lower end thereof, centrally of the sides thereof, as by a mounting shaft H8, is the lower end of a cylinder I853 of a hydraulic piston and cylinder assembly, indicated generally by the reference numeral Iill. The hydraulic piston and cylinder assembly ISI has a piston rod m2 which. is adapted to be extended and retracted vertically. The upper end of the piston rod W2 is flexibly mounted within a support block 533, which block Hi3 is secured, as by a bolt Hi l, to a transversely extending angle member N35. The angle member I85 is the lower movable clamp element or jaw member of the clamping device of my present in vention, and is adapted to be moved toward and away from the fixed upper jaw member W5. A vertical slot 85 is formed in the plate member I10 and the bolt Ida, provided for securing the support block N33 to the lower jaw member 85, is disposed therethrough for guiding the lower jaw member I 85 in vertical movement. In order to maintain the lower jaw member IE5 at right angles, with respect to the support block member 583, and parallel to fixed jaw I75, a guide pin I8? is mounted in the support block I83 and the lower jaw member ltd below the bolt Hi l. The guide pin I8? is adapted to project into the vertical slot 35 formed in the plate member Hit. The guide pin 53?, like the bolt I84, is adapted to slide vertically within the slot I86 when the piston rod N33 is extended or retracted.

The rear supporting plate Ill has a U-shaped cutout lQil adjacent the upper end thereof, which cutout I530 is provided for receiving the head of bolt it l when the movable jaw I85 is in its re tracted position, as shown by dotted lines in Figure 7.

A pair of openings i5; are formed in the plate member HQ adjacent each side of the hydraulic piston and cylinder assembly ici. Fluid hose lines (not shown) are adapted to be disposed through the openings ISI for connecting the hydraulic piston and cylinder assembly I with a source of fluid under pressure.

A pair of load engaging frame members I are disposed along the lower edges of the plate member Ilil, one adjacent each side thereof. Each of the frame members I95 has a transversely extending slot I36 formed therein. The frame members E95 are supported by means of a pair of spaced bolts E9? which are disposed through the slots I95 and are threaded into the plate member Illl. It will be observed that the frame members I95 may be spread laterally by sliding the brackets 595 along the bolts I97 and may be fixed in any desired location by tightening the nuts I91.

Each of the frame members I95 is formed with forwardlyprojecting portions I98 adjacent the outer ends thereof, at the upper and lower portions thereof. The forward surfaces of the projecting portions 193 are adapted to lie substantially flush with the plate member I18.

The mating surfaces of the fixed and movable jaw members H5 and I85 are cross scored or serrated and are particularly adapted for engaging the leading edges or lips of cardboard containers. It will be understood, however, that the clamp construction is also adapted for gripping the projecting edges of other forms of containers, as, for example, the end boards of wooden crates.

When the leading edge of a container islyin laterally outwardly of the plate member As shown in Figure 8, a pair of clamp constructions, of the type illustrated in Figures 6 and '7, may be mounted to the truck in side by side relation, thereby providing a larger gripping and supporting area which, in turn, provides increased load engaging capacity. It will also be observed that the outermost frame members 595 may still be spread laterally for supporting a container at points lying laterally outwardly of the plate members are.

While I have shown and described what I believe to be certain preferred embodiments of my present invention, it will be understood that various modifications and rearrangements may be made therein without departing from the spirit and scope of my present invention.

I claim:

1. For use with an industrial truck havinga mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending frame means adapted to be mounted to the load supporting carriage transversely thereof, a fixed clamp element being secured to said frame means adjacent the upper edge thereof, movable clamp means disposed vertically below said fixed clamp element and being carried by said frame means, means carried by said frame means for moving said movable clamp means in a. vertical plane toward and away from said fixed clamp element for clamping the upper edge of a load therebetween, and

said frame means having a substantially vertical load engagin surface for preventing rocking movement of a load gripped between said clamp means and said clamp element.

2. For use with an industrial truck having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending main frame means adapted to be mounted to the load supporting carriage transversely thereof, vertically extendin secondary frame means mounted to said main frame means vertically thereabove, movable clamp means carried by said secondary frame means, means carried by said secondary frame means for moving said movable clamp means in a vertical plane toward and away from the upper edge of said main frame means for clamping the upper edge of a load therebetween, and said frame means having a substantially vertical load engaging surface for preventing rocking movement of a load gripped between said clamp means and the upper edge of said main frame means.

3. For use with an industrial truck having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending main frame means adapted to be mounted to the load supporting carriage transversely thereof, vertically extending secondary frame means mounted to said main frame means vertically thereabove, a pair of movable clamp elements carried by said secondary frame means, and means carried by said secondary frame means for moving said pair of clamp elements toward and away from the upper edge of said main frame means.

4. The combination of claim 3 wherein said last named means comprises a pair of hydraulic piston and cylinder assemblies.

5. For use with an industrial truck having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending frame means adapted to be mounted to the load supporting carriage transversely thereof, horizontally extending fixed clamp means secured to said frame means adjacent the upper edge thereof, horizontally extending movable clamp means disposed vertically below said fixed clamp mean and being carried by said frame means, means for effecting movement of said movable clamp means toward and away from said fixed clamp means in a vertical plane for clamping the upper edge of a load therebetween, said last named means being carried by said frame means within the confines thereof,

and said frame means having a substantially vertical load engaging surface for preventing rocking movement of a load gripped between said movable clamp means and said fixed clamp means.

6. The combination of claim 5 wherein said last named means comprises a hydraulic piston and cylinder assembly.

7. The combination of claim 5 includin laterally shiftable load engaging frame members slidably mounted to said frame means adjacent each side thereof along the lower edge thereof for engaging a load laterally outwardly of the sides of said frame means.

8. For use with an industrial truck having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending frame means adapted to be mounted to the load supporting carriage transversely thereof, said frame means defining a horizontal fixed clamp element adjacent its upper edge, vertically movable clamp means carried by said frame means, vertically extending means carried by said frame means for moving said movable clamp means in a vertical plane toward and away from said fixed clamp element for clamping the upper edge of a load therebetween, and said frame means having a substantially vertical load engaging surface depending from said clamp element for preventing rocking movement of a load gripped between said clamp means and said clamp element.

9. For use with an industrial truck having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending frame means adapted to be mounted to the load supporting carriage transversely thereof, said frame means defining a fixed clamp element adjacent its upper end, vertically movable clamp means carried by said frame means, means carried by said frame means for moving said movable clamp means in a vertical plane toward and away from said fixed clamp element for clamping the upper edge of a load therebetween, the mating surfaces of said clamp element and said clamp means extending transversely of the truck, and said frame means having a substantially vertical load engaging surface for preventing rocking movement of a load gripped between said clamp means and said clamp element.

10. For use with an industrial trucl; having a mast and a load supporting carriage movable therealong, load engaging means comprising, vertically extending frame means adapted to be mounted to the load supporting carriage transversely thereof, said frame means defining a fixed clamp element adjacent its upper end, upwardly and downwardly movable clamp means carried by said frame means, means carried by said frame means for moving said movable clamp means toward and away from said fixed clamp element for clamping the flap of a load which projects away from the load and extends transversely of the truck therebetween, the mating planar surfaces of said clamp element and said clamp means extending transversely of the truck, and said frame means having a substantially vertical load engaging surface for preventing rocking movement of a load gripped between said clamp means and said clamp element.

11. The combination of claim 10 wherein said means for moving said movable clamp means toward and away from said fixed clamp element comprises vertically extending hydraulic piston and cylinder means.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,900,569 Lederer Mar. 7, 1933 2,399,360 Lacey Apr. 30, 1946 2,447,300 Williams Aug. 17, 1948 2,475,367 Avery July 5, 1949 2,500,055 Baker Mar. 7, 1950 2,545,021 Coupland et a1 Mar. 13, 1951 2,590,355 Turner et a1 Mar. 25, 1952 2,620,937 Halloran Dec. 9, 1952 FOREIGN PATENTS Number Country Date 582,680 Great Britain Nov. 25, 1946 

